Converts a String in hexadecimal to an Integer

Arduino_hex_to_int.cpp

uint32_t htoi( String htoi_str ){
  char itoh_lower[18] = {"0123456789abcdef"};       // 16 chars + null
  char itoh_upper[18] = {"0123456789ABCDEF"};       // 16 chars + null
  uint32_t htoi_number = 0;
  for(int index = 0; index < htoi_str.length(); index ++){        // each hex number in String
    for(int val = 0; val < 16; val ++){                           // each possible value
      if (  htoi_str[htoi_str.length() -index -1] == itoh_lower[val] ||
            htoi_str[htoi_str.length() -index -1] == itoh_upper[val] ){
        if(val > 0){
          // htoi_number += val * power(16, index);
          htoi_number += (uint32_t)( val * (power(16, index) + 0.01) );
        }
      }
    }
  }
  return (uint32_t)(htoi_number);
}

/*#################################################################################################*/
// alternative version without double to uint32_t conversation

uint32_t htoi( String htoi_str ){
  char itoh_lower[18] = {"0123456789abcdef"};       // 16 chars + null
  char itoh_upper[18] = {"0123456789ABCDEF"};       // 16 chars + null
  uint32_t htoi_number = 0;
  for(int index = 0; index < htoi_str.length(); index ++){        // each hex number in String
    for(int val = 0; val < 16; val ++){                           // each possible value
      if (  htoi_str[htoi_str.length() -index -1] == itoh_lower[val] ||
            htoi_str[htoi_str.length() -index -1] == itoh_upper[val] ){
        if(val > 0){
          htoi_number += val * power(16, index);
        }
      }
    }
  }
  return (uint32_t)(htoi_number);
}

// because pow() is of type double and conversation from double to unit32_t is lossy
uint32_t power(int p_base, int p_exp){
  uint32_t pow_ret = 1;
  for(int p_ctr = 0; p_ctr < p_exp; p_ctr ++){
    pow_ret *= p_base;
  }
  return pow_ret;
}